why clincher more pricey???

[Wyatt Earp]

I'll get the popcorn.....

 

 

 

Spidey' date=' I thought you said earlier that popcorn was inappropriate for this thread We need beer and biltong

 

 

 

Thanks Jeremy for doing all the calculations . Your answers have come the closest to helping me understand how much of a difference rotational mass makes to cycling performance.

 

 

 

 

 

 

 

[/quote']

 

[GoLefty!!]

 

Edmund R. Burke Ph.D

 

Much like his mentors and associates' date=' Dr. Burke gained worldwide renown. Professionals in the fields of exercise physiology, nutrition and medicine are familiar with his exceptional work ethic and reputation as an author, scientist and educator. His 39 page curriculum vitae speaks for itself as it reveals some of his outstanding career accomplishments, including over 1,000 articles and many book chapters and books that he wrote and published in the areas of health, sport science and applied physiology. He served as Coordinator of Sports Sciences for the U. S. Cycling Team leading up to the Olympic Games in 1996 and was a staff member for the 1980 and 1984 Olympic Cycling Teams.

 

Some of his books: http://www.pickabook.co.uk/typesearch.aspx?Type=authorisbn&Code=9781583331460&Key=Edmund%20R.%20Burke

 

Also:

 

"Kiwi, you posted the full force equation. If you substiture values into this equation for wheels of different Ir (rotational inertia) but the same mass, and calculate acceleration, it will show that Ir  has a very very small effect on everything. "

 

Different wheels with different Ir are different because their mass is different. Looking at the table I posted you can see a lighter wheel has a lower Ir and a heavier wheel such as the mountain bike wheel at the other end of the table has a higher Ir.

 

Rotational Inertia and Mass for Various Wheels

 

 

Wheel	Details	Ic (kg m^2)	Mass (gm)
Wire Spoke	Rear, Std Rim, 700, track, 36 spokes, w/o tire, w/ axle, nuts	0.0528	1177
Wire Spoke	Front, Std Rim, 700, 32 spokes, w/ tire, tube, rim strip, axle, skewer	0.0885	1264
Wire Spoke	Rear, Std Rim, 700, 32 spokes, w/12-21 cassette, tire, tube, rim strip, axle, skewer	0.0967	1804
Specialized tri-spoke	Front, 700, w/ tire, tube, axle, skewer	0.0904	1346
Specialized tri-spoke	Rear, 700, w/ 12-21 cassette, tire, tube, axle, skewer	0.1032	1771
Specialized tri-spoke	Front, 650, w/ tire, tube, axle, skewer	0.0683	1207
Mavic	Front, Std Rim, 650, 28 Bladed Spokes, w/ tire, tube, rim strip, axle, skewer	0.0632	1179
MTB	Front, 32 Spokes, w/ tire, tube, rim strip, axle, skewer	0.1504	1847

I'm not suggesting anyone should believe me, this is something very easy to find out for yourself. Strap on some wheels in the 1800 gram range, do a race, then strap on something in the 1400 gram range and do a race and you can feel the difference. As I suggested do the above with a power meter and you can measure the difference.

[/quote']

 

funny this, I recently did just that by trying out a pair of american Classic carbon clincer 58 vs my Easton EA90SLX

 

theres a full 500 gr difference between the wheel sets

 

 

I could feel absolutely no dfference at all.

 

What I could feel is that the AMC carbon 58's rolled nicer than the easton's.

 

This is clearly a scientific arguement for heavier wheels.

 

BTW, I'm with Bornman on this one.

Even though differences in Ir and all that makes great calculation and keesp my HP48Gx busy, out on the road those little difference are lost in the total package on the road.

 

Get wheels that are sturdy, and have machined braking surfaces. I've seen so many come a cropper while using carbon tubbie rims and then could not stop because the braking performance was inconsistent.

 

oh btw, Por's are paid to ride their equipment

 

[TNT1]

39 page CV huh? When you're a ponce, you're a ponce...

[GoLefty!!]

like bling, there are no half measure of ponce

[Barend de Arend]

 

Jules has made the following comments:

C: I reckon aerodynamics is a far more important concern than mass

at the perimeter of a wheel.

A: I dare not go into aerodynamical calculations (they are

horrific and usually non-linear and only solvable by numerical

means)' date=' but I would tend to agree with you here.

 

[/quote']

 

It's a very different exercise.

 

• Aero is squared.  Twice the speed is four times the drag.

• Aero is drag.  It needs constant work -- not just to accelerate.  That alone should make a bigger impact.

• Aero changes in crosswinds.

• In a bunch, aero is less important than solo, or in a break when you're sharing the work.  It's not going to make a difference at the back of the bunch.  But then you're not attacking, either.

• Just like weight, aero of the rider has a larger factor than aero of the wheels or bike.  I think that the percentages are very different though.  ie. aero wheel is a larger percentage of the total package than a lightweight wheel's percentage of total weight.

Excellent work!

 

 

[Jules]

 

In a bunch' date=' aero is less important than solo, or in a break when you're sharing the work.? It's not going to make a difference at the back of the bunch.? [/quote']

 

 

 

Yebo yes. I remember Cervelo did some sums showing why their Soloist was faster than the R3 even on steep mountain passes. They said that the aerodynamic advantage of the soloist outweighed the weight advantage of the R3.

 

 

 

However, I remember thinking that they did not specify whether they were referring to a rider in a bunch or in a break.

[GoLefty!!]

most aero numbers are quoted from data gathered by testing aero components under static conditions in a wind tunnel. The data does not translate well to the road since effects of wind direction change are not taken into account.

 

At the end of the day, aero, lighter weight are all just tools to get a customer to hand over more money for an item that has low intrinsic value.

 

Just get the goodies that looks the best.

 

I'm all over the proper bike fit thing at the moment.

 

proper fit has a much bigger effect on your performance on the bike than does aero wheels or lighter wheels. Thats the best R250=R450 you can spend.

With this information I've come to realise that way too many peopleare willing to spend loads of cash to simply look pro. Thats fine but then why try to get all scientific about looking good?

 

[TNT1]

 

 

Just get the goodies that looks the best.

 

 

 

 

Spoken like a true roadie.

 

[GoLefty!!]

well you can't look half pretty can you?

 

does you wife so half her make up?

 

do you get half a hair cut?

 

or wear half underpants? [lightbulb]

 

 

 

[TNT1]

 

 

or wear half underpants? [lightbulb]

 

 

 

 

I second the motion... Is the prototype ready yet?

 

[GoLefty!!]

it was, but the other half binned them. Said they needed replacing.

[jmaccelari]

 

 

BTW' date=' I'm with Bornman on this one.

Even though differences in Ir and all that makes great calculation and keesp my HP48Gx busy, out on the road those little difference are lost in the total package on the road.

[/quote']

And I'd also agree with you. Maths ain't everything.

 

The energy saving really is less than 1%. What you probably noticed

was the inertia of the wheel. This (simplistically) is the resistance of

the wheel to changes in its rotational velocity (speed).

 

You took more energy (a very small amount) to spin them up and then

it felt more comfortable (like a flywheel) during the race since they

continued to roll more easily and smoothly.

 

The whole package is about more than just weight...

jmaccelari2010-01-04 21:38:27

[epoh]

I think it is time to put the biltong, popcorn and coke away. The time has come to print and snort this thread and enlighten ourselves!  

[BikesRxS]

Pure Genius Johan, we have been suckered into this weight weenie nonsense for too long and need to change our beers. Well done man, hope some of the hubbers have the cranial capacity to get what you saying

 

Cheers .

 

Excellent start to 2010 !

 

[LazyTrailRider]

Hmmm, one question no one has asked yet: what happens when you have a couple of patches on your tube (like I always have) and you ride a R2000 wheelset (like I do), with tyres constantly gunked with dirt?

 

Will I never be able to win a race, ever?!

[TIMEprb]

OK' date=' I think your averages vary far too much. If I work with these I have to ask you how much you accellerated for each attack from 1 to 24. Too much work. Give me an average attack speed and lets pretend on this race the attacks were all equal.

 

Scenarios (actual data)	Time (s)	Acc m/s2
Scenario One 33 to 63 in 30 sec	20	0.277778
Scenario Two  33 to 67 in 55 sec	25	0.171717
Scenario Three 36 to 72 in 55 sec	30	0.186869
Scenario Four  30 to 76 in 65 sec	35	0.324786

 

 

Have a look at the far right colum. This is accelleration for the said scenario in m/s/s or m/s2

 

Choose one and we go with that.

 

 

[/quote']

 

Just a little nit picking...<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />

 

How the hell did a cyclist accelerate @ 200 m.s^2 when gravitational acceleration is but 9.8 m.s^2 ????

 

Your calculations are based on a load of bull Mr Wise Guy!

 

Using your most modest figure, this guy completed 90km in 30 sec

 

To clarify

 

s=ut+1/2at^2 (physics law of movement)

 

Say the guy does 0km/h and starts accelerating @ 200m.s^2

 

u = 0 (initial speed)

t = 30 (time)

a = 200 (acceleration)

 

Pop those into the equation and you end up with a total distance of wait for it

 

90 km in 30 seconds amazing!!!!